Transparent glue should be printed with UV ink (that is, UV curing ink).

Matters needing attention in transparent self-adhesive printing:

First, the pressure problem:

Printing pressure has a great influence on printing quality. Maintaining uniform and constant printing pressure in the effective printing area can not only make the ink color of printed matter uniform, but also make the size of printed matter stable. The maximum printing pressure can be obtained by flat pressing. However, due to the problems of manufacturing accuracy and smoothness of printing plates, as well as the uneven thickness and pressure of self-adhesive substrate, the printing quality is affected. One of the measures to solve the uneven pressure is to make a gasket, where the pressure is small, the lower part of the workbench will be padded; First, appropriately reduce the hardness of flexography. However, this is limited to reduce the hardness of flexography. If the flexographic hardness is too low, the geometric dimensions of graphics and texts will expand outward, and small fonts will be blurred easily. When printing in a large area, the problem of printing pressure is not easy to solve. Therefore, we borrow the method used in bronzing, that is, put a layer of silicone rubber plate with 175 line and hardness of 90 on the workbench, which can solve the problems of insufficient exhaust and large local pressure.

Second, paste the version.

Small characters, such as fonts below size 8, often have dry ink on them because of the small spacing between thin lines, which causes unclear adhesion between pictures and texts. This is mainly because the ink dries too fast. Our company now uses resin offset printing ink produced by an ink company in Shenzhen, which is sticky and has high temperature, so the ink dries quickly. The printed products are very fine self-adhesive printing products, and there are many dry printing phenomena. In this case, the first thing to do is to find the problem from the flexible resin version itself. It is generally required that the bottom of the resin version of the font feels smooth and not sticky. However, due to insufficient exposure, the bottom of the font is sticky and soft, which is easy to stick to ink, and the ink accumulates and dries up in thin lines. If discarded, it will waste plates. At this time, resin plate post-treatment liquid can be used. The post-treatment solution contains sodium hypochlorite and hydrochloric acid, which can harden the radical and eliminate the problem of stickiness. The most fundamental way is to find out the accurate exposure time and make a standard resin version. It is recommended to use a copper-zinc version with a particularly fine font. It is not easy to dry ink between copper and zinc fonts, and the fonts are hard, so it is easier to print clear strokes. In terms of operating environment, attention should be paid to reducing air flow. If it doesn't work, we can add an appropriate slow-drying agent to the ink to slow down the drying speed. Increasing the printing speed relatively properly can prevent the ink from being excessively dried.

Halo: Cloudy shadows sometimes appear on self-adhesive products, which is mainly caused by uneven distribution of ink. The inking roller of the plane pressure-sensitive adhesive printing machine is a chrome-plated iron roller with a diameter of 150mm, which can move axially back and forth. Its function is to receive ink from the ink fountain roller and the ink transfer roller, evenly mix the ink, and then transfer it to the ink transfer roller. When the ink transfer roller loses its ink transfer function, it is easy to form vignetting. In addition, the ink roller is vulcanized by soft nitrile rubber. If you don't pay attention to maintenance, the inking effect will decrease, and it will also cause vignetting. Solving vignetting is to solve the problem of uneven distribution of ink, and the ink supply can be increased appropriately.

Fourthly, the synchronization of die-cutting and printing.

Self-adhesive label printing generally needs to be cut into a certain shape before use. In a die-cutting press, the synchronization of die-cutting and printing is very important. The up-and-down movement of die cutting and the up-and-down movement of printing table are driven by the main transmission shaft, so there is synchronization. The cutting position is determined by the double crank structure to control the rotation distance of the traction roller, so it is very important to adjust the crank radius and the pressure of the platen.

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